Plasma Modification Of Alumina For Thermal Interface Material

Thermal interface materials (TIM) is key material to improve heat transfer from the heat source to heat sink by reducing the thermal contact resistance caused by the air pockets between two contacting surfaces. A crucial problem that high thermal conductivity and low modulus hardly achieved balance was brought out in producing the high performance elastomer TIM. In this paper, a series of SiR/Al2O3 composites were prepared. To achieve the guidance of preparing high performance of TIM, the filler surface modification process, the modulus and thermal properties of composites were studied. Thermal conductive mechnasim was developed. Some interesting results were found as followed:1. Coupling agent KH-570 had more positive effect than KH-550 during the surface modification of alumina.When KH-570 used with plasma in treatment, the modulus of SiR/Al2O3 composite got lower in pace with elongation of plasma treatment time and increasing of plasma treatment power.Although KH-570 can lower the modulus of composite to some extent, a better modification agent was needed.2. A novel method was developed that alumina filler was first coated by LSR by solution dispersion and subsequently treated by argon cold plasma. The modified a-alumina fillers were characterized with HRTEM, TGA, FTIR, and XPS. The results revealed that a thin PDMS film several nanometers thick was tightly coated on the surface of the alumina filler after plasma treatment. The amount of tightly coated LSR (i.e., CR(tight)) varied with the plasma treatment time and power. The optimal coating time was found to be 2h and optimal coating power was 90W. SiR/Al2O3 composite was prepared, the payne effect was characterized with RPA. It was found that modification of alumina with LSR coating and plasma treatment can dramatically weaken the strength of the filler-filler networks and lower the modulus of the SiR/alumina composite. This modification would not change the thermal porperties of composite.3. Dispersion of filler, interface between filler and matrix and payne effect of composite were characterized with SEM and RPA. The results revealed the main reason for modulus lower was that the LSR film could avoid the direct contact of fillers. Same thermal conductivity dicipline was found according to different filler loading using treated and untreated alumina. Experiment results illustrated that the heat conduction path can form without filler contact. The nano-film of LSR would not block the formation of heat path. This result was different with traditional machnism.